WO-A1-85/05553 discloses bacterial cell surface proteins having fibronectin, fibrinogen, collagen and/or laminin binding ability. Thereby it is shown that different bacteria have an ability to bind to fibronectin, fibrinogen, collagen and/or laminin. It is further shown that fibronectin binding protein derived from Staphylococcus aureus has a molecular weight of 165 kD and/or 87 kD, whereby it is probable that the smaller protein is a part of the larger one.
Fibronectins are a family of high molecular weight glycoproteins occurring in a soluble form in many body fluids and in an insoluble form as a compound of cell surfaces, basement membranes, and extracellular matrices. Fibronectins appear to fulfil a critical role in clearance by phagocytes of autologous tissue debris, immune complexes, and bacteria. Fibronectins also bind to epithelial cells. In doing so it may serve as a receptor for organisms like group A streptococci, but may also shield the epithelial receptors of other organisms. Thus the inability of Gram negative organisms like Ps. aeuruginosa to colonize the oral cavity of healthy humans may be due to an interference in binding to epithelial receptors by fibronectin. The ability to resist binding to soluble fibronectin has been thought to be a virulence factor in invasive infection by group B streptococci. A number of Gram positive bacterial species including Staphylococcus aureus, other staphylococcus species, and group A, C and G streptococci exhibit specific interaction with fibronectin. In these species binding to fibronectin is thought to be a virulence factor enhancing colonization of wound surfaces and other fibronectin coated surfaces. E. coli can express a variety of adhesins with differing binding specificities. The majority of these adhesins recognize carbohydrate moieties present on glycoconjugates. E. coli may also express binding to matrix proteins such as fibronectin, laminin, and collagen. Uropathogenic E. coli expressing the 075 X adhesin bind tubular basement membranes and to the Bowman capsule known to be rich in laminin. The purified 075 X adhesin was specifically found to bind laminin. E. coli isolated from patients with ulcerous colitis frequently bind matrix proteins Likewise, E. coli isolates from bovine mastitis have been shown to bind to fibronectin at a high frequency. Below a native fibronectin binding protein from E. coli is disclosed, as well as the cloning of the fibronectin binding, fnbA gene from a bovine isolate of E. coli that express curli pili and fibronectin binding when present in E. coli HB101.
Chemically fibronectin is a large glycoprotein (M.sub.r about 450 kD) with two similar subunits, which may vary in molecular size depending on a complex splicing pattern of a precursor mRNA. The major function of fibronectin which is found in body fluids blood clots and extracellular matrices seems to be related to the ability of the protein to mediate substrate adhesion of most eukaryotic cells.